Magnetic memory device



A ril 6, 1965 w. J. SCHOENMAKERS 3,177,473

MAGNETIC MEMORY DEVICE Filed Jan. 21. 1960 INVENTOR WIJNAND J. SC HOENMAKE RS 5;... z. AGE T United States Patent 3,177,473 MAGNETEC MEMORY DEVICE Wijnand Johannes Schoenmaliers, Eindhoven, Netherlands, assignor to North American Philips Company, Inc, New York, N.Y., a corporation of Delaware Filed Jan. 21, 1960, Ser. No. 3,968 Claims priority, application Netherlands, Feb. 26, 1959, 236,551 2 Elaims. (Cl. 340-174) The present invention relates to magnetic memory devices comprising at least one filamentary member of magnetic material having a rectangular hysteresis loop, which member is coupled to several control conductors at discrete distances.

A memory device of this type, also termed twistor, is for example described in the Bell System Technical Journal, November 1957, pages 1319 to 1340, and may be used in computers or automatic signalling systems for storing binary information in the form of given characteristic states of magnetisation of given parts of the wire in the proximity of the locations where it is coupled to the control conductors. The wire may, for example, be twisted so as to produce internal mechanical stresses and a preferential direction of magnetisation in the material, which magnetisation follows helical lines, the pitch of which subtends an ang e of 45 with the axis of the wire. Since, consequently, the magnetisation has a component at right angles to the wire axis, it is variable by means of a current through the wire itself and, conversely, an induction voltage in longitudinal direction of the wire is produced by magnetisation variations. If desired, the wire may be wound at a given pitch onto a core of electrically conductive material. Such memory devices have the advantage over devices with ring-cores that the coupling to the control conductors is simpler in manufacture. It may, for example, be effected by means of windings surrounding the magnetic wire or by causing the control conductors to cross the magnetic wire at right angles and at a short distance, whereas in the case of ring-cores the control conductors have to be slipped through the aperture of the core, which particularly in view of the usually small size of these cores is not simple since the insulation of the control conductors is jeopardized.

The storing of information at definite points of the wire in the proximity of the control conductors may, for example, occur by simultaneously applying a pulse to the wire and to particular control conductors, this pulse having such a strength that the current through the wire and through the control conductors is in itself insufficient to change the magnetisation in the wire, since in this case the magnetic field strength remains below the value of the coercive force, whereas at the location where it is coupled to the control conductors to which pulse is applied, the magnetisation changes on account of the coercive force there being surpassed by the joint action of the two pulses. If the couplings to control conductors lie comparatively close together, which is desirable for minimizing the size of the memory devices, there is a risk, on applying a pulse to definite control conductors, that the magnetisation also changes in the proximity of couplings to other control conductors, due to the magnetisation in the wire proceeding too far.

The present invention has for its object to mitigate this disadvantage.

According to the invention, short-circuit conductors are provided around the magnetic wire at discrete distances.

In order that the invention may be readily carried into effect, an example will now be described in greater detail with reference to the accompanying drawing which represents diagrammatically a matrix memory device according to the invention.

3,177,473 Patented Apr. 6, 1965 Referring to the drawing, a number of wires M1, M2 and MS of electrically-conductive magnetic material are provided having a rectangular hysteresis loop. A number of control conductors B1, B2 and B3 are coupled to the several magnetic wires through windings W11, W12, W21 and so on. The magnetic wires are twisted in known manner so as to produce, as stated before, a preferential direction of magnetisation at an angle of approximately 45 with the axes of the wires. Binary signals can be stored independently of each other at several points of one and the same wire in the proximity of the couplings to the several control conductors by imparting to these points a given characteristic state of magnetisation, which may be effected in known manner by simultaneously applying a pulse to the magnetic wire and to the pertinent control conductors. Reading out of the signals formation may, for example, occur by applying a pulse of opposite direction to a magnetic wire, the points where the information is stored being magnetised in opposite direction and a pulse being produced in the coupling windings coupled to said points.

In this device, a difliculty is experienced. If, for example, a storage pulse is applied to the conductor B2 and to the magnetic wire M1 for storing information in the proximity of the coupling winding W12, whereas no pulses are supplied to the conductors B1 and B3, due to the current in the winding W12, the magnetisation of the Wire in the proximity of the windings W11 and W13 is yet affected to a degree, since the field variation propagates over a certain distance along the wire. According tothe invention, this inconvenience is obviated by providing the magnetic wires with electrical short-circuiting rings K11, K12, K21 and so on between the points where the magnetic wires are coupled to the control conductors. Any variation of magnetisation in the proximity of these shortcircuiting rings induces a current in these rings, the direction of which is such that the variation of magnetisation is counteracted, thus preventing the variation of magnetisation from extending beyond the rings.

What is claimed is:

1. A magnetic storage device comprising a filamentary member of electrically conductive magnetic material having a rectangular hysteresis loop, a plurality of spaced apart control conductors coupled to said member, and short-circuited conducting means surrounding said member between each adjacent pair of said control conductors and spaced therefrom.

2. A magnetic storage device comprising a wire of electrically conductive magnetic material having a rectangular hysteresis loop, means for twisting said wire, a plurality of spaced apart control conductors inductively coupled to said wire, and means for limiting propagation of magnetic field along said wire comprising short-circuited conducting means surrounding said wire between each adjacent pair of said control conductors and spaced therefrom.

References Cited by the Examiner UNITED STATES PATENTS 1,778,894 10/30 Fry 20091.2 2,945,217 7/60 Fisher et al 340---174 2,979,701 4/61 Marchand 340-474 FOREIGN PATENTS 205,776 3/59 Austria. 431,793 11/11 France.

IRVING L. SRAGOW, Primary Examiner.

EVERETT R. REYNOLDS, JOHN T. BURNS,

Examiners. 

1. A MAGNETIC STORAGE DEVICE COMPRISING A FILAMENTARY MEMBER OF ELECTRICALLY CONDUCTIVE MAGNETIC MATERIAL HAVING A RECTANGULAR HYSTERSIS LOOP, A PLURALITY OF SPACED APART CONTROL CONDUCTORS COUPLED TO SAID MEMBER, AND SHORT-CIRCUITED CONDUCTING MEANS SURROUNDING SAID MEMBER BETWEEN EACH ADJACENT PAIR OF SAID CONTROL CONDUCTORS AND SPACED THEREFROM. 